In the glassware decorating industry, there exists the desire to apply one or more layers of a suitable material in various predetermined patterns to an article for decorative or other purposes. One of the important commercial applications today is in the printing of bottles having a generally cylindrical configuration. The term "cylindrical" as used herein is intended to cover articles, e.g., bottles, which have at least one portion which is characterized by a cylindrical cross-sectional shape, e.g., substantially circular or round. The aforementioned bottles have found a wide variety of applications, for example, cosmetics, perfumes, food products, household and personal cleansing products, etc. One application which is believed to dominate the present market in terms of volume is beverage bottles for both soft and alcoholic beverages.
There is known a variety of apparatuses for decorating bottles with multiple colored printing inks for forming decorative predetermined patterns and/or textured material. For example, it has been common practice to decorate cylindrical shaped bottles using a screen printing apparatus which includes a conventional reciprocating screen printing assembly. In the known reciprocating screen printing assembly, a generally rectangular frame supports a patterned screen which carries the printing ink to be screen printed onto the underlying article by means of a squeegee. In one such type of screen printing assembly, the screen is held stationary while the squeegee is moved across the surface of the screen in order to force the printing ink through the screen thereby creating the desired pattern. In another screen printing assembly, the screen is reciprocated laterally while maintaining the squeegee stationary in engagement with the surface of the screen. Illustrative of the aforementioned screen printing assembly are those disclosed in Poo, et al., U.S. Pat. Nos. 4,068,579; Walker, 4,091,726; Eldred, et al., 4,263,846; Lala, 4,282,806; Cammann, 4,352,326; Okura, 4,380,955; Combeau, 4,434,714; Heidenreich, 5,317,967; Carlyn, et al., 5,343,804; and Strutz, et al., U.S. Pat. No. 5,524,535 the disclosures of which are incorporated herein by reference.
In addition to the aforementioned reciprocating screen printing assemblies, there is known from Von Saspe, U.S. Pat. No. 3,933,091 a screen printing apparatus employing a stationary semi-circular printing screen using a rotatable squeegee assembly having a plurality of squeegees. There is further known from Coningsby, U.S. Pat. No. 4,628,857, a screen printing apparatus including a horizontally arranged rotary screen printing assembly. The screen printing assembly is operative for printing a non-continuous coating on a substrate of various shapes such as cylindrical, conical or oval, in particular, slender-like articles such as writing implements. The screen printing assembly is in the nature of a cylindrical hollow printing drum provided with an opening for accommodating a patterned screen. The interior of the drum includes a squeegee and a supply of printing ink. Articles to be screen printed are placed on a conveyor and moved to a position underlying the screen at which time the article is lifted by an elevator mechanism into engagement with the continuously rotating screen printing drum. The disclosures in U.S. Pat. Nos. 3,933,091 and 4,628,857 are incorporated herein by reference.
In Duce, U.S. Pat. No. 4,885,992 there is disclosed a vertically arranged indirect rotary screen printing assembly particularly adapted for printing spark plug insulators, the disclosure of which is incorporated herein by reference. The screen printing assembly includes a vertically arranged screen printing drum provided with a printing screen and an internal squeegee. The screen is arranged in contact with a transfer roller having a transfer surface. The image to be transferred is first applied to the transfer surface and, upon rotation of the transfer roller, to the surface of the intended article such as the spark plug insulator. The use of a vertical screen printing assembly avoids having to index articles to be printed from an initial vertical supply orientation to a horizontal printing orientation, and then back again to a vertical discharge orientation.
The economics of the bottle screen printing industry are directly related to production rate. Conventional reciprocating screen printing assemblies are known to achieve production rates of only about 180 bottles per minute. In the lucrative beverage bottle decorating industry, it is desirable to obtain production rates of at least 250 bottles per minute, and preferably 500-700 bottles per minute, and optimally up to 1000 bottles per minute. These production rates cannot be achieved by the aforementioned reciprocating screen printing assemblies. In addition, the conventional reciprocating screen printing assemblies, due to their stroke length, e.g., up to about 36 inches, occupy a substantial space within the screen printing apparatus. As a result, the space provided for curing the screen printed ink is often inadequate, rendering the aforementioned screen printing apparatus generally undesirable for multi-colored screen printing operations where curing is required between screen printing workstations, and in particular, where high production rates are desired. This becomes more significant when screen printing multiple registered layers of a printing ink which requires overprinting of one layer with the next layer without the adverse consequences of streaking of the previously applied layer.
In Von Saspe, production rates of up to 220 bottles per minute are disclosed using the stationary semi-circular screen printing assembly. However, the screen printing apparatus of Von Siaspe requires multiple drying tunnels which occupy a large portion of the screen printing apparatus, and hence, floor space which might not always be available.
A number of the aforementioned disadvantages from the known screen printing apparatus are overcome by the screen printing apparatus disclosed in U.S. patent application Ser. No. 432,485, filed on May 1, 1995, and assigned to the same assignee of the present application the disclosure of which is incorporated herein by reference. The disclosed reciprocating screen printing apparatus arranges a UV radiation source opposing the printing screen at each screen printing workstation. Articles to be decorated are positioned between the UV radiation source and the printing screen. Each article is printed with an image formed from a UV curable composition by being rolled across the printing screen. The UV radiation source is positioned so that as the applied image is transferred to the article, UV radiation is incident upon the article's surface as it rolls away from the printing screen with the newly transferred image. The image is exposed to the UV radiation for a sufficient duration such that a cured skin forms on the surface of the transferred image of sufficient strength to support the next layer to be applied to the article. The disclosed screen printing apparatus has a production rate of up to about 180 bottles per minute.
Notwithstanding the known screen printing apparatus, there remains a need for a screen printing apparatus and decorating method therefore which is operable for printing UV curable compositions in various patterns and/or registered layers directly onto articles having cylindrical portions at a production rate heretofore unknown from the prior art, while at the same time, providing for the at least partial cure of the UV curable composition between one or more screen printing workstations.